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EFIT Design and Transient Analysis M. Schikorr, E. Bubelis EUROTRANS: DM1 WP1.5 : “Safety”

EFIT Design and Transient Analysis M. Schikorr, E. Bubelis EUROTRANS: DM1 WP1.5 : “Safety” Madrid , 13-14 November 2007. Topics:. Design Criteria for EFIT-Pb 2. EFIT design data for Transient Analysis 3. Some EFIT-Pb results to the ULOF transient.

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EFIT Design and Transient Analysis M. Schikorr, E. Bubelis EUROTRANS: DM1 WP1.5 : “Safety”

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  1. EFIT Design and Transient Analysis M. Schikorr, E. Bubelis • EUROTRANS: DM1 WP1.5 : “Safety” • Madrid , 13-14 November 2007 EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  2. Topics: • Design Criteria for EFIT-Pb 2. EFIT design data for Transient Analysis 3. Some EFIT-Pb results to the ULOF transient EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  3. 1. Some important EFIT Design Criteria: • Use of MgO-based MA-MOX Fuel Mixture • Operate EFIT at k_eff ~ 0.95 - 0.97 with flat k_eff burnup characterisitics • Adopted 3-Core region design to obtain flat radialpower profile (designed by ENEA and ANSALDO) • Design core and primary system in such a manner to allow sufficient natural convection flow rate to sustain a ULOF transient for at least 30 minutes without „large number“ of pin failures (via gas blowdown) • Account for burn-up and protective oxide layer formation during operation of plant EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  4. EFIT ULOF Design Criteria requires : Assure a sufficiently large natural convection flow rate ( > 25 % nominal flow) under ULOF-ss conditions. This implies : 1. keep pressure drop across the core „low“ (~<0.75 bar) by selecting an appropriate fuel pin / subassembly design 2. minimize pressure losses throughout the primary / DHR system such that total system pressure loss <~ 1.0 – 1.1 bar 3. assure a height differential between the core midplane and the heat sink midplane of at least > 2.00 m EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  5. Keeping DP_core in the XT-ADS Design low: • Select an appropriate pin / sub-assembly design by optimizing the pin diameter, pin pitch, wrapper dimensions etc. • Minimize the number of grid-spacers and optimise design • Keep the length of the fuel pin low • Optimize inlet and outlet support structures to keep pressure drops small EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  6. Most current EFIT Design Data: Inner Core Region, Core Zone 1 EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  7. Most current EFIT Design Data: Intermediate Core Region, Core Zone 2 EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  8. Most current EFIT Design Data: Outer Core Region, Core Zone 3 EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  9. Other EFIT Data Inputs: 854mm lower gas plenum 274mm upper gas plenum EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  10. EFIT-Pb: Avg and Peak Cladding and Fuel Temperatures at Nominal and ULOF-ss Plant Conditions for BOC and EOC EOC state is defined to be max burnup ~ 100 MWd/kg of MOX-MA fuel EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  11. ULOF: BOC, Peak Pin, 6 Spacer @ 0.50mm thickness 2. ULOF: EOC, Peak Pin, 6 Spacer @ 0.50mm thickness, 100 um oxide EFIT ULOF Transient Cases Analysed: EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  12. EFIT-Pb : ULOF, BOC, Peak Pin, 6 Spacer @ 0.50mm thickness, no oxide Conclusion: For current design EFIT peak pin clad will NOT fail under BOC conditions even though of flow undershoot that is ~ 22 % nom. flow. Min Clad Failure Time ~ 17 hours EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  13. EFIT-Pb : ULOF, EOC, Peak Pin, 6 Spacer @ 0.50mm thickness, 100um oxide Conclusion: For current design EFIT peak pin clad will most likely NOT fail under EOCconditions even though of flow undershoot ~ 22% (min. clad failure time ~ 1000 sec). Peak pin fission gas pressure will be </~ 100 bar. EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

  14. 1.) The ULOF transient is less sensitive in the Pb-cooled EFIT design than to the XT-ADS design because of its better natural convection characterisitcs: (38% of nominal flow for EFIT-Pb compared to ~ 25% nominal flow for the XT-ADS under ULOF-steady state conditions). 2.) The current design of the Pb-cooled EFIT system achieves the design goal of sustaining a ULOF transient for at least 0.5 hours without pin failures. Conclusions on EFIT ULOF Transient : EUROTRANS WP1.5 Safety Meeting : Madrid, Nov 13-14. 2007

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